CNDP1 and type 2 diabetes mellitus: Similar to our previous studies (Zhang et al. 2019; Zhou et al. 2021), serum CN-1 concentrations in T2DM patients with poor or intermediate renal function (eGFR < 60 ml/min/1.73m2) were significantly lower as compared to those with good renal function (eGFR ≥ 60 ml/min/1.73m2), but the latter patients had higher serum CN-1 concentrations compared to healthy controls (Fig. 1d).